The present invention is directed to a machine for fabrication of roof trusses and, more particularly, to an automatic control system for such a machine for fabrication of roof trusses. A number of additional features and objects will be apparent in connection with the following discussion of preferred embodiments and examples.
Pitched roofs are commonly supported by roof trusses. Roof trusses are commonly constructed of wood, particularly for wood-framed structures and residences. Roof trusses are manufactured in a wide variety of shapes and sizes according to the needs encountered in erecting a specific building. Because the roof line is usually fairly uniform throughout much of the length of a single building, many identical trusses are needed for a single building.
It has long been known that such trusses can be fabricated more efficiently through use of a truss table than they can by manual methods at the job site. The truss table is setup so that each precut piece of a particular truss fits into a channel created by parallel raised members fastened to the top of the truss table. When all the pieces for a single truss have been put in place on the truss table, they are fastened together. Nails, staples, and other similar fasteners have long been used. For some time, it has been common practice to fasten many of the joints, particularly those bearing greater loads, with connector plates, which consist of a flat plate having a large number of downward projecting parallel spikes generally created by pressing a flat plate within a specially designed die. A connector plate is seated on both the top and bottom sides of the joint as the truss lies on the truss table.
The connector plates may be seated by hammering or the like. Substantial forces are required to seat the connector means of a machine.
A truss fabricating machine includes a gantry movable along an X-axis and a pressing cylinder suspended from the gantry which is movable along the Y-axis allowing the pressing cylinder to be located above a joint in a wooden truss. The pressing cylinder presses down to seat connector plates into selected joints of the truss. A joystick generates electrical signals proportional to the direction and extent of movement of the joystick by the operator, which are converted to pulse width modulated electrical signals in a driver, whose output controls proportional solenoids that drive infinite positioning four-way hydraulic valves to actuate hydraulic motors that drive the gantry and pressing mechanism along either the X-axis, or through a separate hydraulic circuit, the Y-axis. The pressing cylinder can be moved along both axes simultaneously. When the pressing cylinder is in the desired position, a thumb switch on top of the joystick is actuated, causing the ram of the pressing cylinder to descend until it seats the connector plate. Releasing the thumb switch causes the ram to move upward to the top of its stroke.
What is needed is an automatic or partially-automatic control system for such a truss fabrication machine to enhance the efficiency and ensure the maintenance of quality standards in the fabrication of trusses.